merged introductions

spec/Section 1 -- Overview.md

@@ -9,13 +9,41 @@ and complexities of the underlying distributed systems are hidden. The
 observable behavior of the distributed GraphQL executor is the same as that of a
 standard GraphQL executor as described by the GraphQL specification.
 
+GraphQL Composite Schemas specification has a number of design principles:
+
+- **Composable**: Rather than defining GraphQL schemas in isolation and
+  reshaping them to fit a composed graph later, it encourages developers to
+  think of GraphQL schemas as partial schemas that are designed as part of a
+  larger schema from the get go. Each source schema defines the types and fields
+  it is responsible for serving within the context of a larger schema,
+  referencing and extending what is already there. In other words, the GraphQL
+  Composite Schemas specification is not designed to glue arbitrary schemas
+  together, but to facilitate a coordinated effort to build a coherent composite
+  schema.
+
+- **Collaborative**: The GraphQL Composite Schemas specification is explicity
+  designed around team collaboration. By building on a principled composition
+  model, it ensures that conflicts and inconsistencies are surfaced early and
+  can be resolved before deploying. This allows many teams to contribute to a
+  single schema without the danger of breaking it.
+
+- **Evolvable**: A composite schema offers an integrated, product-centric view
+  of underlying services. And these services should be able to evolve without
+  disrupting clients. Over time, the same functionality may be provided by a
+  different combination of services, while the schema surface stays the same.
+  Source schema boundaries are therefore considered an implementation detail and
+  should never be exposed to clients.
+
+- **Explicitness**: This specification values explicitness over inferring
+  intentions, as these tend to break down and can lead to ambiguity over time.
+
 This specification focuses on two core components to allow interoperability
 between tooling and gateways from different implementers, the schema composition
 and the execution.
 
-- **Composition**: The schema composition describes a process of merging
+- **Composition**: The schema composition describes the process of merging
   multiple source schemas into a single GraphQL schema that is annotated with
   execution directives and is referred to as the composite schema.
 
 - **Execution**: The distributed GraphQL executor specifies the core execution
-  behavior and algorithms.
+  behavior and algorithms.

spec/Spec.md

@@ -83,7 +83,7 @@ Note: This is an example of a non-normative note.
 
 # [Overview](Section%201%20--%20Overview.md)
 
-# [Subgraph](Section%202%20--%20Subgraph.md)
+# [Subgraph](Section%202%20--%20Source%20Schema.md)
 
 # [Supergraph](Section%203%20--%20Supergraph.md)